[PATCH 0/2] vfio: constify struct class usage

[PATCH 0/2] vfio: constify struct class usage

[Ricardo B. Marliere]

This is a simple and straight forward cleanup series that aims to make the
class structures in vfio constant. This has been possible since 2023 [1].

---
[1]: https://lore.kernel.org/all/2023040248-customary-release-4aec@gregkh/

To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>

---
Ricardo B. Marliere (2):
      vfio/mdpy: make mdpy_class constant
      vfio/mbochs: make mbochs_class constant

 samples/vfio-mdev/mbochs.c | 18 ++++++++----------
 samples/vfio-mdev/mdpy.c   | 18 ++++++++----------
 2 files changed, 16 insertions(+), 20 deletions(-)
---
base-commit: 87adedeba51a822533649b143232418b9e26d08b
change-id: 20240301-class_cleanup-vfio-3c5f72230ba5

Best regards,
-- 
Ricardo B. Marliere <ricardo@marliere.net>

[PATCH 1/2] vfio/mdpy: make mdpy_class constant

[Ricardo B. Marliere]

Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the mdpy_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
---
 samples/vfio-mdev/mdpy.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 72ea5832c927..27795501de6e 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -84,7 +84,9 @@ static struct mdev_type *mdpy_mdev_types[] = {
 };
 
 static dev_t		mdpy_devt;
-static struct class	*mdpy_class;
+static const struct class mdpy_class = {
+	.name = MDPY_CLASS_NAME,
+};
 static struct cdev	mdpy_cdev;
 static struct device	mdpy_dev;
 static struct mdev_parent mdpy_parent;
@@ -709,13 +711,10 @@ static int __init mdpy_dev_init(void)
 	if (ret)
 		goto err_cdev;
 
-	mdpy_class = class_create(MDPY_CLASS_NAME);
-	if (IS_ERR(mdpy_class)) {
-		pr_err("Error: failed to register mdpy_dev class\n");
-		ret = PTR_ERR(mdpy_class);
+	ret = class_register(&mdpy_class);
+	if (ret)
 		goto err_driver;
-	}
-	mdpy_dev.class = mdpy_class;
+	mdpy_dev.class = &mdpy_class;
 	mdpy_dev.release = mdpy_device_release;
 	dev_set_name(&mdpy_dev, "%s", MDPY_NAME);
 
@@ -735,7 +734,7 @@ static int __init mdpy_dev_init(void)
 	device_del(&mdpy_dev);
 err_put:
 	put_device(&mdpy_dev);
-	class_destroy(mdpy_class);
+	class_unregister(&mdpy_class);
 err_driver:
 	mdev_unregister_driver(&mdpy_driver);
 err_cdev:
@@ -753,8 +752,7 @@ static void __exit mdpy_dev_exit(void)
 	mdev_unregister_driver(&mdpy_driver);
 	cdev_del(&mdpy_cdev);
 	unregister_chrdev_region(mdpy_devt, MINORMASK + 1);
-	class_destroy(mdpy_class);
-	mdpy_class = NULL;
+	class_unregister(&mdpy_class);
 }
 
 module_param_named(count, mdpy_driver.max_instances, int, 0444);

-- 
2.43.0

[PATCH 2/2] vfio/mbochs: make mbochs_class constant

[Ricardo B. Marliere]

Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the mbochs_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
---
 samples/vfio-mdev/mbochs.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index 93405264ff23..9062598ea03d 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -133,7 +133,9 @@ static struct mdev_type *mbochs_mdev_types[] = {
 };
 
 static dev_t		mbochs_devt;
-static struct class	*mbochs_class;
+static const struct class mbochs_class = {
+	.name = MBOCHS_CLASS_NAME,
+};
 static struct cdev	mbochs_cdev;
 static struct device	mbochs_dev;
 static struct mdev_parent mbochs_parent;
@@ -1422,13 +1424,10 @@ static int __init mbochs_dev_init(void)
 	if (ret)
 		goto err_cdev;
 
-	mbochs_class = class_create(MBOCHS_CLASS_NAME);
-	if (IS_ERR(mbochs_class)) {
-		pr_err("Error: failed to register mbochs_dev class\n");
-		ret = PTR_ERR(mbochs_class);
+	ret = class_register(&mbochs_class);
+	if (ret)
 		goto err_driver;
-	}
-	mbochs_dev.class = mbochs_class;
+	mbochs_dev.class = &mbochs_class;
 	mbochs_dev.release = mbochs_device_release;
 	dev_set_name(&mbochs_dev, "%s", MBOCHS_NAME);
 
@@ -1448,7 +1447,7 @@ static int __init mbochs_dev_init(void)
 	device_del(&mbochs_dev);
 err_put:
 	put_device(&mbochs_dev);
-	class_destroy(mbochs_class);
+	class_unregister(&mbochs_class);
 err_driver:
 	mdev_unregister_driver(&mbochs_driver);
 err_cdev:
@@ -1466,8 +1465,7 @@ static void __exit mbochs_dev_exit(void)
 	mdev_unregister_driver(&mbochs_driver);
 	cdev_del(&mbochs_cdev);
 	unregister_chrdev_region(mbochs_devt, MINORMASK + 1);
-	class_destroy(mbochs_class);
-	mbochs_class = NULL;
+	class_unregister(&mbochs_class);
 }
 
 MODULE_IMPORT_NS(DMA_BUF);

-- 
2.43.0

Re: [PATCH 0/2] vfio: constify struct class usage

[Alex Williamson]

On Fri, 01 Mar 2024 14:51:46 -0300
"Ricardo B. Marliere" <ricardo@marliere.net> wrote:

> This is a simple and straight forward cleanup series that aims to make the
> class structures in vfio constant. This has been possible since 2023 [1].
> 
> ---
> [1]: https://lore.kernel.org/all/2023040248-customary-release-4aec@gregkh/
> 
> To: Kirti Wankhede <kwankhede@nvidia.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
> 
> ---
> Ricardo B. Marliere (2):
>       vfio/mdpy: make mdpy_class constant
>       vfio/mbochs: make mbochs_class constant
> 
>  samples/vfio-mdev/mbochs.c | 18 ++++++++----------
>  samples/vfio-mdev/mdpy.c   | 18 ++++++++----------
>  2 files changed, 16 insertions(+), 20 deletions(-)
> ---
> base-commit: 87adedeba51a822533649b143232418b9e26d08b
> change-id: 20240301-class_cleanup-vfio-3c5f72230ba5
> 
> Best regards,

Applied to vfio next branch for v6.9.  Thanks,

Alex